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Thread: gaerbox issues

  1. Default gearbox issues

    Car makes a clanking noise which may relate to the gearbox/slip diff. Car has had a refurb recently after not been driven much. Timing belt etc but gearbox not removed just oil changed with one recommended by Honda. The mechanic I use says it could be the slip diff and not sure if a normal gearbox shop could actually do any refurbs. It almost feels as if something is sticking.

    Sorry I am not technically minded but would appreciate any feedback. Could it be as simple as the oil?

    Thanks in advance

    1996 N Plate manual
    Last edited by bainsgs; 31-05-2022 at 11:25 AM.

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    Diagnosing the noise issue over the web is one of the most difficult thing based on my experience.

    Quite often, the source of the noise was completely different from the place/parts that the person described.

    You could upload the video file but not easy to diagnose without listening to the noise with having the car in front.

    The position of the microphone, sound reflection due to surrounding environment, the equipment used for recording/playback, etc all changes the sound frequency, direction, etc.


    Changing the oil (MTF) would change the sound frequency depending on the oil spec but if it was replaced with the one recommended by Honda, then it would be the Honda MTF-3.

    You already have one of the best option for the street usage.


    You can also inspect the MTF meshed metal filter on the trans case but probably not much use for your case if the noise is really from the DF (differential).


    You can do basic investigation by listening for the noise under the following conditions but from what you wrote, best if you can take your NSX to someone with the actual experiences with the NSX Gbox.

    In the past, something reported as gbox noise was actually from the drive shaft, wheel bearing, loose wheel nut on refurbished wheel as the coating melted after spirited driving and even the cause was from the engine and not the Gbox.


    All conditions with the engine running;
    In neutral, 0mph, CL (Clutch) engaged (CL pedal up).
    In neutral, 0mph, CL disengaged (CL pedal floored).
    Drive on straight line at moderate speed, go through each gears to check any noise difference.
    Make 90deg Left and Right turns at crawling speed. Any difference between turning left or right?


    I won't go too much into technical detail but for your reference, from 95+, NSX started using the torque reactive style LSD with the helical planetary gears, etc.

    Unlike the 91-94 LSD of steady pre-set breakaway torque, the 95+ LSD would increase the pressure force against the pre-loaded multiple friction discs resulting in much higher breakaway torque.


    Kaz

  3. Default

    Kaz,
    Thanks for that. In neutral there is no noise, clutch engaged and disengaged. When you put it in first or reverse noise starts quickly but not constant as if something is rotating and then catching. In the Midlands if anybody knows of anybody with experience of the NSX G box. I will double check the oil spec.

    Gurinder

  4. #4

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    Quote Originally Posted by bainsgs View Post
    Kaz,
    Thanks for that. In neutral there is no noise, clutch engaged and disengaged. When you put it in first or reverse noise starts quickly but not constant as if something is rotating and then catching. In the Midlands if anybody knows of anybody with experience of the NSX G box. I will double check the oil spec.

    Gurinder
    My 91 Nsx recently developed the same noise as you described, rolling speed forward or backward, noise coming from left hand side/ Gearbox. No noise when car is off the ground. Car starts fine, butter smooth select in any gear. Had the passenger side driveshaft inspected by a mechanic but found nothing abnormal.

    Gurinder, please report back if you managed to fix your and ill do the same.

    Phil

  5. Default

    Will do. They did use the MTF-3 oil so nothing untoward there

  6. #6

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    Hi Kaz, Where is the MTF meshed metal filter located?

    Phil

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    The location.



    If the noise is from the DF, probably inspecting the strainer won't tell much.

    There is a big magnet plate near the MTF pump so any big particles would be trapped there.

    At the strainer, normally you would only see tiny particles from the synchro or gear teeth edge or anything that doesn't stick to the magnet such as the liquid gasket.






    You'll need the replacement o-ring and the MTF filler washer.

    The drain washer is the same one used at the oil pan/sump drain.

    If never done before, good idea to get spare cover as you could break the tab.








    If not treated in the past, by now, the blue section of the strainer cover is already heavily oxidised and bonded to the trans case.

    This makes the removal of the cover time consuming if not done previously.

    On installation, just coat the blue section and the backside of the tab with the silicone grease.

    Never apply leverage force trying to lift the cover using the tab marked in red.

    Instead, apply force in the direction marked in yellow to 'rotate' the cover back and forth.

    This will break the oxidation and while trying to rotate the cover, change the direction of the force just a little to pull the cover outwards.

    Repeat it and eventually, it will come off.






    The example of what you would expect inside the strainer.

    Just a tiny metal bits with metal powder.






    The worst one so far….. It's not metal and in fact, excessive amount of liquid gasket.


    Kaz

  8. #8

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    Thank you Kaz��

  9. #9

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    So just a little update on my side. I replaced the diff oil from Honda MTF-3 to Royal Purple and the noise had disappeared.

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    Thank you for the update, Phil.

    Interesting. OEM DF (differential) or aftermarket one???

    I know fair amount of owners in US used 'cocktail' mix for the MT oil when they experienced difficulty in gear shifting.
    For me, this is just hiding the issue and not a fix because for street driving, one should not have any shifting problem with the Honda MTF3.

    Some even reported new issue on DF by using the cocktail method despite the significant improvement on the shifting difficulty.


    The earlier spec DF has multiple CL disks with embedded friction material and soaked in the MTF.
    It's pre-loaded and constant locking force regardless of the input force difference between the R & L shaft.
    The spring washer/plate sets the friction force and the locking won't start slipping/break out until after exceeding the pre-loaded torque.

    So, using different MT oil will change the characteristic of the locking/slip behaviour.
    For the clarification, this doesn't mean good or bad on the DF friction disks.

    Would be interesting to hear the update in longer term as I know some owners in Japan are using customised RP fluid in their MT box.


    Kaz

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